Apparatus for gas turbines



P 3, G. JENDRA S S IK 2,213,939.

APPARATUS FOR GAS TURBINES I Filed June 25, 1938 lm/enfor:

Patented Sept. 3, 1940 I t "UNITED STATES PATENT OFFICE 2,213,939 APPARATUS FOR GAS TURBINES George Jen'drassik', Budapest, Hungary Application June 25, 1938, Serial No. 215,811 In Hungary June 26, 1937 2 Claims. (@l. 6041) Gas turbine proposals are known in which the matical sectional drawing of a gas turbine plant output of the gas turbine is controlled by varyshown, by way of example, Fig. 2 shows both (flat ing the temperature of the working iiuid entering and steep) types of pressure-volume compressor the turbine, that is to say by varying the quancharacteristic, and, finally, Fig. 3 is the image,

5 tity of heat introduced. In. some of these prodeveloped into a plane, of a section taken throughv 5 posals preferably a heat exchange device serving the blades of a compressor having a steep presfor the transmission of the heat of the gas? sure-volume characteristic. leaving the turbine to the compressed Workir In the apparatus according to Fig. 1 the comfiuidis also p yed. pressor casing l is accommodating the rotor d,

It is a drawback of this method of control that journalled in the bearings 2 and 3, the said rotor 10 by diminishing the quantity of heat introduced, 4 being, through the shaft coupling 5, coupled the temperature of the working fluid expanding with the turbine rotor 9, accommodated in the down in the turbine as well as the back-pressure turbine casing 6 and journall'ed in the bearings l of the compressor and therewith also the pressure and 8. The stationary blade rings IU of the com-- drop of the turbine will also become diminished, pressor are arranged in the compressor casing I, 15 in consequence whereof, besides the deterioration whereas the rotary blade rings ll thereof are of the thermal efiiciency of the apparatus, the mounted in the compressor rotor 4. The staweight of the air supplied by the compressor will tionary blade rings l2 of the turbine are fixed in also become substantially increased. Thus, althe turbine casing 6, whilst the rotary blade rings though by diminishing the quantity of heat intro- 13 of the turbine are fixed in the rotor 9. The 20 v duced it is possible to influence the output of mechanical energy generated can be taken off at Work of the apparatus in the direction of dethe shaft end l4.

- crease, the fact of the quantity of gas flowing In the embodiment shown by way of example through the apparatus having become increased the fuel is introduced by means of the burners or will influence the said output in the contrary atomizers I5, whilst the combustion is effected 25 sense and accordingly will necessitate a greater in the combustion chamber l6. For the purpose diminution of the temperature in order to obtain of transferring the heat of the expanded gases a certain given fractional output whereby the leaving the turbine to the compressed fresh gas, thermal efiiciency will be deteriorated in a still the heat exchange device I 1, shown diagramgreater extent. It is particularly in the case of matically on the drawing, is employed. The 30 compressors possessing a so-called fiat presthrottle-valve 18 serves for the control of the sure-volume characteristic that the circumstance quantity of air admitted into the compressor. referred to becomes troublesome, this being This apparatus operates in the following manner. understood to refer to such compressors in which The air enters the rotary compressor through in the case of the diminution of the over-pressure the duct l9, and leaves the compressor in com- 35 produced the percentual increase of the gas pressed condition through the duct 20. Followvolume supplied is greater than the percentual ing this the air flows through the heat exchange diminution ofthe overpressure. device H, in which it absorbs a portion of the Starting from the recognition of this circumcontents of heat of the spent gases leaving the stance, the invention prescribes the employment, turbine. Following this the air passes into the 40 for gas turbines, of a compressor of such a kind combustion chamber HS, in which the combustion the pressure-volume characteristic of which is at least in part, of the fuel introduced takes place. very steep i. e. with which the variation of the The compressed and heated air enters the turbine back-pressure will in the neighbourhood of the .through the inlet duct 2| and after expanding in ordinary service condition cause the volume of the turbine leaves the latter through the duct 22. 45 air drawn in to become altered in every slight Following this the gas leaving the turbine passes extent only. A gas turbine plant fitted with a into the heat'exchange device ll, where it transcompressor of this type will react in a very scnmits its heat to the fresh air coming from the sitive manner on any variation of the quantity compressor and finally it leaves the apparatus of fuel introduced, and will in the case of varythrough the duct 23. The control of the output 50 ing loads operate at a substantially higher efliof this apparatus is effected by varying the quanciency than a gas turbine plant fitted with a tity of fuel introduced, and in accordance here-, compressor possessing a flat characteristic. with the temperature of the gas expanding in In order to enable the invention to be more the turbine will also be lower in the Case of direadily understood, Fig. 1 illustrates a diagramminished useful output than at full load. In case 55 a compressor of flat pressure-volume characteristic, e. g. some variant of the usual type of centrifugal compressors should be employed by way of compressor, its characteristic would have the form of the curve shown in broken lines on Fig. 2. The ordinate of 1 his characteristic shows the ratio of the overpressure 13-720 produced by the compressor and of the initial pressure 7:0, whilst its abscissa shows the volume of air drawn in per second, and in whatfollows the expression ratio of pressures should always be understood to mean the corresponding figure expressed in terms of overpressure. The curve traced on Fig. 2 relates to a given number of revolutions per minute of the compressor. If the point marked A on the, drawing is the point corresponding to the normal service condition of such a compressor, the volume supplied will in the case of a flat pressure-volume characteristic become increased by e. g. 20% of the normal supply in case of the diminution by 10%,; in the neighbourhood of the normal conditionof service, of the pressure ratio produced. Accordingly, if during the course of.

the control ofthe turbine plant the quantity of heat introduced is diminished in such'an extent as to cause the pressure drop set-up in the turbine being diminished by 10% of the pressure drop corresponding to the condition of normal load, which will approximately be the case if the temperature of the gas entering the turbine becomes diminished from 450 C. to 375 (7., the volume of air drawn in will in the case of a compressor possessing a fiat characteristic become increased in a very substantial extent e. g. by 20% and therefore it is only in a much smaller degree that the useful output of the turbine will diminish, which fact necessitates a further diminution of temperature.

The curve- C-traced in afull line on Fig. 2 represents the characteristic of a compressor of the kind suitable for being employed in an apparatus according to the invention. The ordinate here again represents the pressure ratio produced, whilst the abscissa represents the volume drawn in. In this case a variation of the pressure ratio by 10% in the neighbourhood of the point A corresponding to the normal service condition will only cause a very slight alteration e. g. an alteration by of the volume drawn in by the compressor. Compressors possessing a so steep characteristic are represented by the type of compressors in which the mean diameter of some stationary or rotating blade ring is at least approximatelyof the same magnitude as the average figure ofv the mean diameters of the blade rings adjacent to it and in which the' section of blades is similar to the wing profiles known in aerodynamics. Such a compressor may be of the axial through-flow type, as shown also by way of example on Fig. 1, in which case the working fluid is flowing between cylindrical surfaces, or between" conical surfaces possessing a small apex angle, through the rotating and the stationary blades, but it is also possible .for the compressor to be of the radial throughfiow type, or"

-faces having curved generatrices.

blade rings 24 and 25, respectively, ,whereas the arrow III indicates the direction of theimeridian speed component. The rings 26 and 21 are stationary blade rings. Experience shows that it is possible to construct a compressor possessing a steep characteristic with a very good efliciency by employing an arrangement in which the base lines CC and D-D of the profiles of the stationary and moving blades (the lines traced tangentially to the concave side of the blade profiles), respectively, are forming with the peripheral direction angles B1 and 132 the magnitude of which is situated between the limits of 30-'75, and which two angles are preferably mutually equal. From the point of view of steepness the employment of a large number of stages and of a high peripheral speed is advantageous, but a sufiiciently steep characteristic can already been obtained also by means of four stages.

It is a matter of course that the compressor described in what precedes does not exhaust all the possibilities of the construction of compressors of steep characteristic, but only indicates a single possibility of construction. Y

A further advantage of a compressor of this type is also represented by the fact that it is possible to construct it so as to possess a very high efiicieficy, which fact is of first-rate importance particularly in the case of gas turbine plants. A type of control of very satisfactory efficiency can be obtained in case the compressor is constructed so as to possess a characteristic of suchsteepness} as will, according to what has been said above, ensure that in case of a diminution of the .overpressure corresponding to the normal condition of service by 10% the volume drawn in by the compressor should not become increased by more than 5%. a

The employment of a'compressor possessing a steep characteristic oflers advantages also in that case if it is not purely by varying the temperature i. e. the quantity of heat introduced that control is effected but. if at the same time the quantity of air supply by the compressor is, by means of the throttle-valve I 8 arranged in the inlet duct of the compressor, varied also. In this case the compressor described possessing a steep characteristic is, on the one hand, advantageous owing to its-high efliciency, whilst on the other hand it enables the control to be performed with high efficiency also in such a manner that it of these when effecting the control. In this case also, the employment of a compressor possessing a steep characteristic ofiers an advantage, which advantage however is of course no longer of an as great magnitude as in the case when it is purely by varying the temperature that control is effected.

I claim:

1. In an apparatus for gas turbines preferably fitted with a heat exchange device, a rotary comforming work by means of the expansion of the heated working medium, and blade rings in. the compressor the mean diameter of any of which is at least approximately equal to the average figure. of the mean diameters of the adjacent blade 'pressor, having at least four stages, supplying the working medium under pressure, a turbine perrings, and in which the magnitude of the angles formed on the internal circle of the blades by the base lines of the blade profiles (the lines traced tangentially to the concave side of the blade profiles) with the peripheraldirection is between the limits of 30 and 75 selected so that in it, with a given speed, the decrease by 10% of the normal service overpressure will cause the volume of gas drawn in to be increased in an extent smaller than 5%.

2. In an apparatus for gas turbines preferably fitted with a heat exchange device, a rotary compressor, having at leastfour stages, supplying the working medium under pressure, a device for introducing heat into the compressed working medium, and blade rings in the compressor the proximately equal to the average figure of the mean diameters of the adjacent blade rings, and in which the angles formed on the internal circles of the stationary and ofthe rotating blades by the base lines of the blade profiles (the lines traced tangentially to the concave side of the blade profiles) with the peripheral direction are in each particular compressor stage mutually equal, the said angles being, within the limits of 30 and 75', selected so that in the compressor, with a given speed, thedecreaseby 10% of the normal service overpressure will cause the volume of gas drawn in to be increased in an extent smaller than 5%. v

GEORGE JENDRASSIK. 

